1. Field of the Invention
The present invention relates to an artists' sectional stretcher with canvas.
2. Related Art
As is known, artists stretchers with canvas have hitherto comprised a stretcher part on which the canvas is fixed by means of metal staples or tacks. Fixing of this type takes place at the outer perimeter edge of the stretcher. Such stretchers may fundamentally be subdivided into two types, more specifically rigid or non-expandable stretchers and expandable stretchers having mobile, sides. In the latter there are provided, in the end zones of the sides of the stretchers, mating seats for the ends of the stretcher sides and housing seats for expander elements, in the form of substantially V-shaped springs or wedges, whose purpose is to create an expanding, or spacing, effect between each two adjacent sides of the stretcher, so as to keep the canvas properly tensioned, both during the act of fixing the canvas and subsequently, following the known dilations or shrinkages of the canvases, as are well known in the art. When canvas-tensioning springs are used, the stretchers have also to be provided with right-angled tubular corner-pieces in their corner zones. the stretchers having wedges, by contrast, the tensioning of the canvas takes place manually, as the result of more or less extensive insertion of wedges by percussion in the corner zones of the stretcher.
It is likewise known that all these solutions, while processing specific advantages, likewise possess disadvantages of various types, some of which they possess in common. In the first place, the fixing of the canvas requires a certain skill, a certain strength and, in any event, a long fixing time. The uniformity of the tensioning of the canvas further depends on the skill of the operator. Not all users, in particular young people, students and ladies, are able to apply the canvas correctly. It is further known that, during the drying of the canvas, following moistening thereof as a consequence of the application of paints or as a result of the absorption of atmospheric humidity, unattractive curvi-linear "crescent" deformations occur along the perimeter edges of the stretcher, between adjacent tacks. The gap or distance between the tacks must on the one hand be sufficiently small to reduce such phenomena and permit uniform tesnioning of the canvas, but on the other hand the tacks act like wedges in the stretcher and an excessively short distance between them may result in breakage of the stretcher. During the shrinkage of the canvases on rigid stretchers the latter, particularly if of large dimensions, undergo substantial deformations, which, in turn, comprise zones of slackening and the formation of corresponding creases in the canvases.
It is further known that, in the zones of folding of the canvases in the outer corner zones, three superposed layers of canvas are formed which, in the case of canvases of a certain thickness, for example 1 mm, possess a thickness of 3 mm. Such thicknesses are cumulative on two opposite sides. In expandable stretchers, therefore, their height and width dimensions comprise the height and width values of the stretcher plus said enlargements resulting from the application of the canvas, plus additionally the total stretching or expansion which takes place and which varies from time to time as a function of the type of canvas and of the contractions or dilations thereof. The result of this is that, with equal external dimensions of the stretcher, problems of seating arise, during framing of these expandable stretchers, in the relative seats of the picture frames, in that these seats do not have large tolerances, and in fact are made, for reasons of cost, to be increasingly small or permit only small dimensional tolerances of the stretcher. The result, therefore, is that stretchers that are only slightly expanded fall out of the seating of the respective picture frame, while stretchers which are substantially expanded do not even fit into said seatings, as a result of which it is often impossible to use picture frames of standardized dimensions. It has therefore frequently been found that frames are not disposed to welcome these stretchers that expand by means of corner springs. These springs moreover, acting exclusively in the corner zones, cannot provide the same effectiveness in canvases of small dimensions or of large dimensions, such effectiveness obviously diminishing with the increase in the dimensions of the stretcher. The fixing of the canvas with metal staples or tacks further requires that the sides of the stretchers be made of wood. This material is notoriously subjected to continuous intrinsic deformations and, in the production of expansion-type stretchers, exhibits substantial wastage, for example of the order of 15-20%. Such wastage, combined with the need for special working of the ends of the sides of the stretchers and with the need for wedges or springs for resilient prestressing, and for the angled corner-pieces, entails high production costs. In practice, furthermore, it is not possible for the user to shorten the lengths of the sides of the stretchers purchased, for example in order to create smaller stretchers, in that this would require the subsequent creation by a craftsman, on the new ends, of the end seatings for the connection of the sides of the stretcher, and of the tensioning springs or wedges. Since, moreover, the artist may select canvases of different types, for example made from linen, cotton, plastic fibre, etc, depending for example on the techniques or paints employed, the practical result is that it is wasteful for the producer and retailer to produce and stock a plurality of finished stretchers of different dimensions and with different canvases. Since such stretchers, once assembled, are somewhat bulky, this entails associated problems of storage, packaging and transport. These parameters, which are naturally also reflected in the selling costs, also determine the most convenient type of sale as a function of the market in question. Therefore in markets covering a large area, for example in the United States, Canada, Australia and the like, such stretchers are offered for sale not in a pre-mounted state but in the form of loose stretcher sides of various dimensions. The artist selects these stretcher sides closest to the dimensions of the picture which he intends to paint, and the canvas is selected separately. After assembly of the stretcher, he fixes the canvas with the tacks or staples, which likewise requires the availability of the appropriate tools. In markets of lesser extent, for example in various European countries, the stretchers are offered for sale in the pre-assembled state and with the canvas fixed thereon, generally boxed in packs of, for example, 6 or 12 stretchers for the retailer. This solution would however entail extremely high costs in the event of transportation over long distances, as mentioned above.
A further disadvantage of the knonw expansion stretchers resides in the fact that they can possess only a quadrangular shape, while there is a demand on the market for different form also, for example oval forms. In these cases, the application of means of tensioning the canvas is impossible, and the user has to fix the canvas in the traditional manner, with tacks or staples. A further disadvantage of the known expansion stretchers resides in the fact that, particularly with large dimensions, they require cruciform inserts in order to stiffen them, the practical effeicacy of which is somewhat limited since, as is well known, good stiffening of the canvases is achievable only with corner diagonals.
It is further stressed that any distribution on major markets of expansion stretchers having right-angled corner-pieces and springs would require them to be marketed in the form of kits containing the various components of the stretcher, which, bearing in mind the relevant number of standardized stretcher dimensions, would require a substantial expenditure not only for the machines automatically producing such packaging, but especially in respect of the relevant number of different packagings necessary, their transportation and their storage by the producer and retailer.